A man who triggered a suitcase bomb in a failed attack at a busy Brussels train station was a 36-year-old Moroccan citizen who was known to the police but was not wanted over terrorism-related offenses, the Belgian authorities said on Wednesday.

The bomber entered Brussels Central Station at 8:39 p.m. on Tuesday, went downstairs from the main ticket hall and began shouting near a group of passengers, according to Eric Van der Sijpt, a spokesman for the federal prosecutor’s office.

He was carrying a suitcase bomb that contained nails and gas bottles, Mr. Van der Sijpt said. The man set off a partial and relatively harmless explosion.

He then left the bag behind while he went in pursuit of a station master, Mr. Van der Sijpt said, and it “exploded a second time, more violently.”